Field of the Invention
The present invention generally relates to a touch point correction method for a Double Clutch Transmission (DCT) and, more particularly, to technology that can more suitably correct a touch point that is the clutch characteristic of a DCT in consideration of changes in the temperature and centrifugal force of a relevant clutch.
Description of Related Art
An Automated Manual Transmission (AMT) including a Double Clutch Transmission (DCT) is a system for automatically controlling a manual transmission mechanism. There are many cases where an AMT is configured to transfer engine torque to a transmission mechanism using a dry clutch, unlike a typical Automatic Transmission (A/T) that uses a torque converter and a wet multi-disc clutch.
A dry clutch is controlled by an actuator, which is typically controlled using a Torque-Speed (T-S) curve indicating a variation in the transfer torque of the dry clutch depending on the stroke of the actuator.
Meanwhile, the dry clutch has characteristics wherein transfer torque thereof is greatly changed depending on a plurality of factors, such as the tolerance of each component, abrasion attributable to durability, thermal deformation attributable to high temperature, and a change in the friction coefficient of a disc. Thus, it is difficult to uniformly configure data from the transfer torque of the dry clutch.
However, upon performing a control operation, if the dry clutch does not desirably reflect changes in the characteristics of the transfer torque and then the actuator is controlled either insufficiently or excessively, excessive slipping of the dry clutch occurs, or an impact is applied to the dry clutch. Thus, technology is required for precisely predicting in real time the characteristics of the transfer torque of a dry clutch depending on the actuator stroke and utilizing the predicted transfer torque characteristics for controlling the actuator.
However, in order to predict the torque characteristics of the dry clutch, a driving condition and a restrictive condition for the prediction of characteristics are present. Therefore, it is difficult to detect the characteristics of the dry clutch in real time. In particular, there are more constraints for the touch point of the clutch.
For reference, a touch point denotes an actuator stroke at a time at which electric power starts to be transferred to the dry clutch.
FIG. 1 is a diagram showing the clutch structure of a DCT to which the present invention is applied. In the clutch structure, a first clutch 100 and a second clutch 200 are provided on opposite sides of a center plate 10. The first clutch 100 includes a first clutch plate 20 pressurized by the center plate 10 to receive electric power, and a first pressure plate 30 configured to pressurize the first clutch plate 20 with the center plate 10. The second clutch 200 includes a second clutch plate 50 and a second pressure plate 40. The first pressure plate 30 is configured to, when a first engagement bearing 70 moves to the left, pressurize the first clutch plate 20 with the center plate 10. The second pressure plate 40 is configured to, when a second engagement bearing 60 moves to the left, pressurize the second clutch plate 50 with the center plate 10.
In the past, in order to correct the touch point of any one clutch, the touch point is corrected based only on the temperature of the pressure plate of the relevant clutch, but the touch point is influenced by the temperature of the center plate 10 or the pressure plate of the other clutch. In addition, other components may have different temperature changes. As a result, there is a disadvantage in that a touch point is not sufficiently and suitably corrected by a conventional correction method.
Further, a problem may arise in that the first pressure plate 30, the second pressure plate 40, and the center plate 10 constituting the clutch may be deformed due to an increase in the temperature thereof while the vehicle is traveling, thus causing the cover plate 80 of the clutch to be bent.
It is apparent that, when the clutch is rotating in a state in which the cover plate 80 is bent, the radius of rotation of the clutch is changed due to deformation caused by the temperature increase, and then rotational inertia is also changed due to the change in the radius of rotation.
In the past, there was a touch point correction method considering a change in temperature, but a touch point correction method that considers rotational inertia based on a temperature increase, as described above, has not yet been presented. Then, the present invention is intended to provide a correction method that calculates a change in a centrifugal force based on rotational inertia and engine speed and that also considers the change in the centrifugal force upon subsequently correcting a touch point.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.